Colonoscopy screening coupled with polyp removal (polypectomy) significantly reduces the incidence of colorectal carcinoma. Unfortunately, of the 147,500 new cases of colorectal carcinoma diagnosed in 2003, the American Cancer Society estimates that only 37% of these cases were diagnosed early enough for treatment to offer the best possible prognosis.
Colonoscopy screening should be repeated more frequently for subjects who have previously undergone a polypectomy due to their increased risk of recurrent polyp formation. However, in a follow-up phase of the National Polyp Study, at least 20% of subjects who had previously undergone polypectomies failed to return for their follow-up screening. In a more recent study, where 8,865 subjects who had previously undergone a polypectomy underwent a second colonoscopy screening, 2,704 (30.5%) were diagnosed with recurrent polyps. A statistical analysis based on the data from this report projected that 50% of subjects will have recurrent polyps within 7.6 years. Despite this level of risk, many subjects do not undergo additional screening.
Prior to colonoscopy, including virtual colonoscopy procedures, the colon must be cleansed so the surgeon may see any polyps that exist on the interior wall of the colon. Furthermore, the colon also must be cleansed before radiological or surgical procedures involving the colon. This cleansing generally entails the drinking of one or more laxative solutions. Aqueous solutions of sodium phosphate salts (monobasic and dibasic sodium phosphate), such as FLEET® PHOSPHO-SODA®, are very effective oral laxatives and are extensively used prior to colonoscopy, radiographic procedures, and surgery. For pre-colonoscopy use, a split regimen is often preferred that includes one 45 mL dose given the evening before colonoscopy and a second 45 mL dose given at least three hours prior to the procedure on the following morning.
One of the main reasons subjects cite for avoiding colonoscopy re-screening is the unpleasant taste of these phosphate based laxative solutions. Depending on the study, from 15 to 51% of the subjects report discomfort in the form of nausea and vomiting. The extremely salty taste of the laxative solution is believed to be the cause of this discomfort. Frequently, subjects cannot tolerate the ingestion of the complete initial dose of the preparation, which often prevents them from consuming more than a small portion of the second dose.
Thus, there is an ongoing need for better tasting laxative solutions suitable for pre-colonoscopy colon cleansing. A better tasting pre-colonoscopy laxative could increase subject compliance with re-screening appointments. This increased compliance regarding consumption of the laxative solution could reduce the need for repeat procedures attributable to inadequate colon cleansing. The materials and methods of the present invention provide phosphate salt laxatives that are significantly more palatable than conventional phosphate salt laxatives.